by Claudia Puig, USA TODAY

by Claudia Puig, USA TODAY

A bullet-riddled bloodbath with an all-star cast, Gangster Squad is a lurid and ludicrous Mob thriller that glorifies a gangland lifestyle.

In the last five minutes the film (** out of four; rated R; opens Friday nationwide) shifts gears and offers a tribute to law enforcement. But this tacked-on resolution is as sticky and fake as Sean Penn's make-up job.

Penn plays gangster Mickey Cohen as an over-the-top psycho, lacking any of the charm that the former boxing champ purportedly used to get so many to do his bidding. Cohen was one of the most dangerous Mob bosses, but as portrayed by Penn, with his puttied face and snappy pronouncements, he mostly comes off as laughable.

The story is set in L.A. in 1949 when Cohen brought his Brooklyn-based Mob empire to the West Coast. For a while he seemed to have most key officials in his pocket, including police officers, judges and politicians.

Fearless in the face of Cohen's trigger-happy goons, war hero Sgt. John O'Mara (Josh Brolin) initially appears to be the only honest cop in all of the city. A distant second is Sgt. Jerry Wooters (Ryan Gosling), who distracts his pangs of conscience with wine, women and nightclubbing.

When the police chief taps O'Mara to form a clandestine squad to take down Cohen and dismantle his drug, gambling and prostitution rings, at least a half-dozen officers prove eager to play gangster. The plan is to covertly disrupt Cohen's enterprises by using his own tactics, so the men in blue punch, pummel, shoot, bomb and generally behave like bad guys - in service of a greater good.

The crew he assembles is played by an impressive team of actors that also includes Anthony Mackie, Robert Patrick, Michael Peña and Giovanni Ribisi. Given that this was a notoriously racist LAPD, though, the effort to integrate the squad with a black officer (Mackie) and a Mexican-American (Peña) seems an anachronistic nod to contemporary political correctness.

The story is based on true events, as chronicled in Paul Lieberman's eponymous book. But the screenplay, written by former LAPD detective Will Beall, seems to draw more on other gangster movies than insider knowledge.

In one particularly unlikely scene, O'Mara and Wooters take on a slew of Cohen's heavily armed thugs in a hotel lobby. It's two against about 40. But the cops go in guns a-blazing and somehow manage to dodge all the machine gun fire and pick off most of Cohen's men.

In another hard-to-buy scene, O'Mara's pregnant wife Connie (Mireille Enos) survives a machine gun attack on their house, crawls across the floor and gives birth in a bathtub. The baby pops out looking ready to crawl.

While there is little to recommend this movie - and the excessive gun violence could put viewers off - it does evoke a glamorous era, with close attention paid to period costumes, architecture and set design.

L.A. Confidential still remains the quintessential film about the city in that era. The guys here, appropriately, spend a good deal of time in the less-storied environs of Burbank.

If, as Stephen Colbert has said, "the movies is where Americans learn their history," Gangster Squad is just noisy disinformation.